The boiling point of an aqueous solution is 101.13 ∘C. What is the freezing point?

Question

Consult the table of colligative constants.



freezing point: ___°C

Answer 1

From the change in the boiling point of this solution, which is 1.13º (normal boiling point is 100º), we can find the molality of the solution, and then use that value to find the freezing point.

∆T = mK

∆T = change in boiling point = 1.13º

m = molality of the solution

K = boiling point constant = 0.512º/m

Solving for m, we have ...

m = ∆T / K = 1.13º / 0.512

m = 2.19 m

Now use this value and the same equation to find the change in the freezing point:

∆T = mK

∆T = change in freezing point = ?

m = molality = 2.19 m

K = freezing point constant = 1.86º/m

Solving for ∆T, we have...

∆T= (2.19)(1.86)

∆T = 4.07º

Since the normal freezing point of water is 0º, the new freezing point of this solution is -4.07ºC